Abstract
This study investigated the effect of high pressure homogenization (HPH) (up to 190 MPa) on porcine pepsin (proteolytic and milk-clotting activities), and the consequences of using the processed enzyme in milk coagulation and gel formation (rheological profile, proteolysis, syneresis, and microstructure). Although the proteolytic activity (PA) was not altered immediately after the HPH process, it reduced during enzyme storage, with a 5% decrease after 60 days of storage for samples obtained with the enzyme processed at 50, 100 and 150 MPa. HPH increased the milk-clotting activity (MCA) of the enzyme processed at 150 MPa, being 15% higher than the MCA of non-processed samples after 60 days of storage. The enzyme processed at 150 MPa produced faster aggregation and a more consistent milk gel (G’ value 92% higher after 90 minutes) when compared with the non-processed enzyme. In addition, the gels produced with the enzyme processed at 150 MPa showed greater syneresis after 40 minutes of coagulation (forming a more compact protein network) and lower porosity (evidenced by confocal microscopy). These effects on the milk gel can be associated with the increment in MCA and reduction in PA caused by the effects of HPH on pepsin during storage. According to the results, HPH stands out as a process capable of changing the proteolytic characteristics of porcine pepsin, with improvements on the milk coagulation step and gel characteristics. Therefore, the porcine pepsin submitted to HPH process can be a suitable alternative for the production of cheese.
Highlights
Cheese production grows about 4% per year worldwide [1]
Results showed that the proteolytic activity of porcine pepsin did not change (p>0.05) immediately after high pressure homogenization (HPH) and until the 14th day of storage, when compared with the activity measured for non-processed sample (Fig 1)
During storage, a reduction in proteolytic activity and an increase in milk-clotting activity were observed, especially for the enzyme subjected to 150 MPa
Summary
Cheese is produced using calf rennet as the coagulant, but the tendency to reduce the early slaughter of steers due to their being low achievers in terms of meat production [2], has increasingly limited the use of calf rennet, resulting in an increasing search for enzymes to replace calf rennet. A good coagulant replacer must have high specificity at the pH and temperature commonly used for cheesemaking [3, 4] and a low unspecific proteolysis, to avoid problems like reduction of manufacturing yield (due to loss of small peptides in the step of whey separation) and the appearance of defects on flavour (bitterness) and texture (brittle texture) [5]. The search for substitutes to chymosin produced by GMO is necessary
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